A light-emitting diode arrangement is understood to mean an arrangement including at least one light-emitting diode unit. A light-emitting diode arrangement typically includes a plurality of light-emitting diode units. Such a light-emitting diode arrangement is, for example, part of a projection device with the aid of which luminous images are generated. The respective light-emitting diode units are supplied with current by means of driver units. In projection devices, a control unit defines a value for the current intensity (current intensity value) for the respective light-emitting diode units. Said value is communicated to the driver unit and implemented by the latter. The implementation usually includes the outputting of current pulses in a time sequence, the current intensity of said current pulses corresponding to the current intensity value communicated by the control unit. The control unit in the projection device has the task, for example, of defining the so-called color locus: if a light-emitting diode arrangement has a plurality of light-emitting diodes that emit in different colors, then the color that arises overall can be defined by means of respective current intensity values for the individual light-emitting diode units. The definition of the color locus and also the definition of the intensity of the emitted light are usually effected in the context of a regulation: there is a photosensitive element in an appropriate measuring unit, which photosensitive element receives and measures the light emitted by a light-emitting diode unit. The measurement values are fed to the control unit, and the latter corrects the current intensity value, if appropriate, that is to say that the current intensity value is stipulated to the driver unit in a manner dependent on at least one measurement value.
WO 02/47438 A2 discloses measuring the temperature of light-emitting diodes and feeding the measurement values to a control unit, which then defines an intensity of the emission in a manner dependent on the temperature.
WO 2007/048747 A1 describes the fact that in a driver unit for light-emitting diodes, numerical values fed to the driver unit can be multiplied, wherein an output signal of the driver unit is defined in a manner dependent on the product thus calculated. This serves, in particular, for putting the brightness proportion factors of the individual light sources in a specific ratio relative to one another. That is necessary during variations of the intensity of the emitted light, the proportion factors, in particular, being variable in this case.
The document DE 10 2005 061 204 describes an illumination system in which 3 colored LEDs and one white LED are controlled independently of one another by a controller.
The document DE 10 2004 060 890 describes a motor vehicle headlight element with LED in which the LED is controlled depending on a measurement variable.
The document DE 102 39 449 describes LED luminaires including a plurality of LEDs, the color or brightness variation of which is compensated for.
The document US 2009/0231354 discloses a calibratable regulation of the color emitted by an LED luminaire.
During the operation of a light-emitting diode it is necessary to prevent the latter from heating up excessively, because permanent damage to the light-emitting diode could occur in this case.
On the other hand, it is a task of the control unit to define the color locus and the intensity of the light emitted by the light-emitting diodes. A monitoring of the light-emitting diodes is not included among the tasks to be assigned to the control unit.